The present invention relates to imaging systems using solid state sensors for detecting multiple picture elements, including optical code imagers and cameras. Aspects of the invention are particularly useful in linear sensor-based and two-dimensional sensor-based, handheld readers. More specifically, the present invention relates to reduced form factor imagers.
Optical codes are patterns made up of image areas having different light reflective or light emissive properties, which are typically assembled in accordance with a priori rules. The term xe2x80x9cbar codexe2x80x9d is sometimes used to describe certain kinds of optical codes. The optical properties and patterns of optical codes are selected to distinguish them in appearance from the background environments in which they are used. Devices for identifying or extracting data from optical codes are sometimes referred to as xe2x80x9coptical code readersxe2x80x9d of which bar code scanners are one type. Optical code readers are used in both fixed and portable installations in many diverse environments such as in stores for checkout services, in manufacturing locations for work flow and inventory control and in transport vehicles for tracking package handling. The optical code can be used as a rapid, generalized means of data entry, for example, by reading a target bar code from a printed listing of many bar codes. In some uses, the optical code reader is connected to a portable data processing device or a data collection and transmission device. Frequently, the optical code reader includes a handheld sensor which is manually directed at a target code.
Most conventional code readers are designed to read one-dimensional bar code symbols. The bar code is a pattern of variable-width rectangular bars separated by fixed or variable width spaces. The bars and spaces have different light reflecting characteristics. One example of a one-dimensional bar code is the UPC/EAN code used to identify, for example, product inventory.
Bar codes can be read employing solid state imaging devices. For example, an image sensor may be employed which has a two-dimensional array of cells or photo sensors which correspond to image elements or pixels in a field of view of the device. Such an image sensor may be a two-dimensional or area charge coupled device (CCD) and associated circuits for producing electronic signals corresponding to a two-dimensional array of pixel information for a field of view. A one-dimensional linear array of photodiodes is also known for use in detecting a bar code reflection image, for example, U.S. Pat. No. 6,138,915 to Danielson et al., which is herein expressly incorporated by reference.
It is known in the art to use a CCD image sensor and objective lens assembly in an optical code reader. In the past, such systems have employed complex objective lens assemblies originally designed for relatively expensive video imaging systems. Such systems may have a single sharp focus and a limited depth of field, which along with conventional aiming, illumination and signal processing and decoding algorithms, limits the versatility and working range of the system.
Other known imaging systems are designed primarily for reading optical codes. Such reading systems involve the assembly and alignment of several small parts. These parts may include a lens, an aperture and a 2D image sensor array such as a CCD chip. Such a structure is illustrated, for example, in U.S. patent application Ser. No. 09/096,578 for Imaging Engine and Method for Code Readers to Correa et al. filed Jun. 12, 1998 and assigned to Symbols Technologies, Inc. The Correa et al. application is hereby incorporated by reference herein. A miniature imager adapted for use in a hand mounted code reader is disclosed in U.S. patent application Ser. No. 09/684,514 filed Oct. 10, 2000 to Patel et al., which is herein expressly incorporated by reference.
The design of an imaging system is dependent upon the size of the package in which the imaging system is to be manufactured. Conventional imaging systems which utilize off-the-shelf components are difficult to miniaturize due to the limited selection of off-the-shelf components. Further, due to various optical phenomena in the design of a miniature imager, various tradeoffs between a component size and the quality of a scanned image must be weighed in the selection of components. Additionally, the selection of certain components for an imager may, due to optical phenomena, limit the choice of other components for the miniature imager.
Accordingly, it is an object of the present invention to provide a miniature imager.
It is a further object of the present invention to provide a miniature imager with an optimal selection of components which provides an adequate scanned image while minimizing the physical size and shape, i.e., the form factor, of the imager.
A miniature imager is typically used in portable applications where the miniature imager is incorporated into a handheld device. These handheld devices typically have a limited battery capacity.
It is an object of the present invention to provide a miniature imager which uses a minimum amount of power in the capture and processing of an image.
Conventional imaging systems which employ solid state imagers suffer from a limitation on the distance that a target image can be from the lens of the imager for correct decoding of the target imager. Specifically, in conventional imaging systems the plane of the pixel array of the solid state imager is arranged perpendicular to the optical axis of the focusing lens. Accordingly, the pixels of the solid state imager are all focused on the same spatial plane of the target image. All of the pixel being focused on the same spatial plane severely limits the working range, i.e., the distance between the imaging system and the target image, of the imaging system. If a conventional imaging system has a single fixed focus lens, adjustments between the imaging system and the target image may have to be made in order to properly receive and decode the target image.
It is an object of the present invention to increase the working range of an imaging system.
To provide illumination and to assist in aiming, imaging systems can employ either lasers or light emitting diodes (LEDs). LEDs may be preferred over lasers since the incoherent nature of the LED light source does not produce the speckle noise impact that is produced by lasers. Further, LEDs are more cost effective than lasers due to the ease of manufacturing and packing of LEDs. Additionally, LEDs can be built more compactly and are easier to surface mount than lasers. However, compared to lasers, LEDs are not an ideal point source. Specifically, light produced by an LED is less focused which produces an increased line thickness of the projected light. To reduce the line thickness of the light produced by an LED, many designers place a mechanical slit in front of the LED. However, the mechanical slit reduces the amount of light that is projected by the LED onto an object.
Accordingly, it is an object of the present invention to provide an LED which has a reduced line thickness of the projected light without severely reducing the amount of light projected by the LED.
These objects and features of the invention will be apparent from this written description and drawings.
These and other problems, drawbacks and limitations of conventional techniques are overcome according to the present invention by a method and apparatus for a miniature imager. In accordance with one embodiment of the present invention, the pixel pitch of an imaging array is reduced compared to a larger sized imager while maintaining the instantaneous field of view of each pixel and the area of the aperture compared to larger sized imagers. In accordance with this embodiment of the present invention an imager with a 4 xcexcm pixel pitch can be produced with a detector array length less than or equal to 2 mm. In accordance with one aspect of this embodiment, by staggering alternate rows of pixels by one half pixel relative to each other a one dimensional imager can be produced with a pixel pitch of approximately 3 xcexcm and a detector array length of approximately 0.75 mm.
In accordance with another embodiment of the present invention, an imager is provided which has a very small form factor and can be operated with little or no artificial illumination provided by the imager thereby providing very low power operation. In accordance with this embodiment of the present invention, an imager chip is mounted on an imager board inside of an imager housing. The imager housing forms a dark room around the imager chip thereby enabling the imager to operate without an external seal. In accordance with one aspect of this embodiment the size of the aperture can be increased to thereby minimize and/or eliminate the need for the imaging engine to provide artificial illumination. In accordance with another aspect of this embodiment a low noise imager with a gain is provided to reduce and/or eliminate the need for the imaging engine to provide artificial illumination. In accordance with yet another aspect of this embodiment an imager which provides a nonlinear response, such as a logarithmic imager, can be provided to reduce and/or eliminate the need for the imaging engine to provide artificial illumination.
In accordance with yet another embodiment of the present invention, an imager includes a image sensor and a focusing lens. The imager sensor has an array of pixels in a first plane and the focusing lens has an optical axis in a second plane. The first and second planes are arranged such that they are not perpendicular to each, thereby increasing the working range of the imager.
In accordance with another embodiment of the present invention, a device includes a light emitting diode having a square portion and a rectangular portion, wherein a height and a width of the rectangular portion is not equal to a height of the square portion. The device also includes a bonding pad, wherein the bonding pad is located on the square portion. In accordance with one aspect of this embodiment, the light emitting diode also includes a second square portion, wherein the rectangular portion has a first and second side the size of the height, wherein the square portion is located on the first side of the rectangular portion and the second square portion is located on the second side of the rectangular portion. A second bonding pad is located on the second square portion. In accordance with another embodiment of the present invention, a light emitting diode die includes a rectangular shaped light emitting diode with a bonding pad surrounding the light emitting diode.
The forgoing is intended as a convenient summary of the present disclosure. The aspects of the invention sought to be protected are set forth in the claims.